marker.ps1::Test-CheckoutLockHeld probed only the owner byte at 1 MiB. Since R5b
every joiner the kill-on-close job refused also locks one of the 16 lease bytes
after it, and hermes_cli/update_lock.py::_try_lock treats any held lease as a
held lock. With the owner dead and a leased completion child still running, the
hand-off read the checkout as free, so the R6 release wait ended and the
Desktop's reclaim deleted the marker next to a live mutator.
Lock/Unlock now cover 1+16 bytes in one LockFile (it fails if any byte is held).
marker.sh needs no change: POSIX takes the checkout lock with flock on the whole
file and the lease bytes exist only on win32 (_take_lease).
Tests: a live Windows cell holds only a lease byte (1 and 16) and expects
`held`; a static cell, runnable on Linux, pins the probed range (RED at start:
(1048576, 1)).
review S1
a041e18255